“After an 11-inning game on Wednesday, we thought it would be better to flip-flop [Chad] Gaudin and Joba,” Girardi said before last night’s 4-2 win over the Mariners at Safeco Field. “We will give him the extra rest the next time through.”

Chamberlain will make his next start after tomorrow on eight days’ rest, Aug. 25 against the Rangers at Yankee Stadium in the opener of a six-game homestand. The extra rest is being done to limit Chamberlain’s innings. In spring training, the Yankees set a 140-inning limit on Chamberlain. They aren’t wary of increasing that to some degree, but would rather not have him throw more than 160 (he’s at 121 2/3).

“The bullpen-starter thing will go for a while,” said Chamberlain (8-2, 3.85 ERA in 22 starts), who will be working on regular rest tomorrow. “The innings, I am pretty excited to get rid of that soon. It’s Year 3 and we still have Joba Rules.

“I understand being able to hold it to a number, but I will be happy to get to October and not worry about this.”

Girardi will start A.J. Burnett, CC Sabathia and Gaudin in the three-game series in Oakland on Monday, Tuesday and Wednesday. After Thursday’s day off, the Yankees will go with Andy Pettitte, Burnett and Sabathia in Boston next weekend.

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Alex Rodriguez was in the original lineup last night, but was scratched before batting practice because of back spasms. Rodriguez missed Thursday night’s game with a bruised left elbow, which was still swollen yesterday after being hit with a pitch during Wednesday’s game.

What caused the spasm?

“I have no idea,” Rodriguez said. “Maybe when I got hit [by the pitch], I know I braced myself pretty good.”

Rodriguez, who said he felt discomfort in his back, didn’t believe the spasms were related to his surgically repaired right hip.

Hideki Matsui, who went 4-for-5 with two homers and five RBIs filling in for Rodriguez in the cleanup spot Thursday night, hit fourth again. He went 0-for-4. Jerry Hairston Jr. started at third base for the second straight game and went 1-for-4 with an RBI.

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It’s too late for Brian Bruney to claim his old eighth-inning setup job, but the right-hander has been effective lately. In five August outings he has worked 6 2/3 innings, allowing just one run. He pitched a scoreless seventh inning yesterday.

Bruney worked a perfect ninth Thursday night after Sabathia went eight innings.

“One thing I have seen is that the last three or four games [Bruney] has been down in the zone,” Girardi said. “He is getting real close to being where he was before he got hurt. There have been times when I have thought about him being the eighth-inning guy if I don’t have [Phil] Hughes that day.”

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Girardi said he expects to give Melky Cabrera a day off soon. Cabrera started last night in a 1-for-13 slide. He went 1-for-4 and scored a run. When Cabrera is rested, Hairston will start in center field. … Girardi said it’s a possibility that center fielder Brett Gardner (fractured left thumb) will not return until the rosters increase Sept. 1.

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Girardi didn’t sound eager to add Damaso Marte to his bullpen. Marte is nearing the end of a 30-day rehab assignment and a decision has to be made to activate him from the disabled list or put him back on the shelf, where the left-handed reliever has been since April with an inflamed shoulder.

“His velocity isn’t where we want it to be,” Girardi said. “He can always go back on the DL if we think he needs more time.”